“This strikes me as incredibly fishy and begs a number of important questions,” said Vitter, the ranking member of the Senate Committee of Environment and Public Works.

"The EPA needs to honor the President’s pledge of transparency and release these documents without redaction of the Administrator’s email address – a big first step toward removing the blanket of secrecy in this agency."

As CNSNews.com reported, the EPA late Monday complied with a court order to release emails from secondary or “alias” email accounts used by Jackson. Attorney Chris Horner of the free-market Competitive Enterprise Institute discovered that Jackson was using an email account in the name of “Richard Windsor,” apparently to send messages on the administration's coal policy. Using the alias would shield those communications from Freedom of Information Act (FOIA) requests.

It is unclear, however, if the 2,100 emails the EPA released on Monday came from the "Richard Windsor" account, because the email address was redacted in the release, and replaced with the word “administrator.”

Jackson admitted to using the false identity before announcing her resignation in December. The EPA has said that Jackson had only one secondary account ("Richard Windsor”), which she used for correspondence with EPA officials.

An EPA official told CNSNews.com on Tuesday that the emails released on Monday --which almost entirely consisted of Washington Post news briefs and Google alerts for "Lisa Jackson"--were all from the "Windsor" account.

But Horner says it’s clear that Jackson has at least two secondary accounts: one showing her name in the sent to/from box; and another one that uses the alias “Richard Windsor.” He is now questioning whether the EPA did in fact produce emails from the Windsor account, as the agency says.

The CEI provided CNSNews.com with copies of internal emails sent to EPA staff from one of Jackson's secondary accounts, which reads "message from the administrator" in the sent field. CEI says the emails it received on Monday look like those emails – not the ones that show “Richard Windsor” as the sender. On that basis, CEI believes Jackson had more than one secondary email account.

Vitter questioned why the email address has been redacted in the first place, saying it does not merit a personal privacy exemption that the EPA claimed under FOIA.

"If ‘Richard Windsor’ is no more than a standard work email account, why not share the unredacted versions and prove it to the American public?” Vitter said.